Field:
This disclosure is concerned generally with the treatment and storage of platelet preparations. More specifically, the disclosure is concerned with incubating platelets under time and temperature conditions sufficient to enhance the overall morphology and function of the platelets prior to use in treating patients needing platelets.
Prior Art:
Platelets are minute, generally flattened formed bodies found in blood. They are essential to the blood clotting process. Platelets can be easily separated from whole blood via simple centrifugation steps. Platelet concentrates so obtained have been routinely administered to platelet-deficient patients. The infused platelets can be obtained from a single unit of whole blood. More often, however, they are "pooled" with other platelet concentrates to provide sufficient platelet quantity for therapy. The platelets from up to 10 units of blood are commonly pooled to provide a single platelet product suitable for infusion. Such pooling is often accomplished using blood bags especially designed for this purpose and is well known to those skilled in the art.
A preferred platelet pooling system provides for the removal of relatively small amounts of residual white blood cells (WBCs) and red blood cells (RBCs). This allows a platelet-deficient patient on component therapy to receive only that blood component actually needed. In addition, this reduces the likelihood of undesirable febrile reactions that may be attributed to WBCs. A platelet pooling bag capable of removing WBCs and RBCs is disclosed in co-pending patent application Ser. No. 585,793 filed Mar. 2, 1984, in the names of S. Wada et al and assigned to the assignee of this application. See also the bag of similarly assigned Ser. No. 788,993 filed in the name of W. Lewis.
Further information on platelets in general and their storage and use can be found in Platelet Physiology and Transfusion, A Technical Workshop, AABB, 1978. All of the above are incorporated by reference into this disclosure.
It is well known that platelets can be stored at room temperature and this is a common practice. Under such conditions, platelets can be stored for up to 5 to 7 days before infusion. This is especially the case if such storage is in gas permeable blood bags that, by virtue of their CO.sub.2 /O.sub.2 gas transmissibility feature, help maintain the pH of a platelet preparation at about 6.8 to 7.2. See, for example, U.S. Pat. No. 4,280,497 to R. Carmen et al.
It has long been thought that storage of platelets at elevated temperatures (e.g. significantly above room temperature or at 37.degree. C.) should be avoided. This is due to an expected increase in metabolic activity, leading to greater acid production and pH fall. Earlier studies have consistently indicated that storage at room temperature is generally preferred. Accordingly, except for cases where platelets are inadvertently warmed in transit, they have not been subjected to any particular heating step or heating treatment for any known purpose prior to infusion. In fact, common accepted practice appears to teach away from any prolonged heat treatment of platelets.
I have now found that a controlled heat treatment of platelets at some point prior to infusion results in improved platelet morphology. The results of the heat (incubation) treatment are quite surprising in several respects. Details of these findings are described below.